Heat exchanger system

ABSTRACT

A heat exchanger system is provided with at least one heat exchanger for heating the suction gas between the evaporator and the compressor inlet, which heat exchanger is heated by the refrigerant liquid. It is the object to achieve dry suction gas from a flooded evaporator. It is an object to achieve heat exchange with a minimum flow restriction. The objects can be fulfilled by a heat exchanger including a circulating path for the suction gas and for the refrigerant liquid. Hereby it can be achieved that the circulating path forms a highly effective heat exchanger. The circulating path can be achieved with a very large heat-transmitting surface. The circulation of the suction gas will force liquid particles in the suction gas to be forced outside in the circulating path and in that way come in direct thermal contact with the surface that separates the suction gas from the refrigerant liquid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to PCT Application No. PCT/DK2021/050111, having a filing date of Apr. 15, 2021, which is based DK Application No. PA 2020 70232, having a filing date of Apr. 15, 2020, the entire contents both of which are hereby incorporated by reference.

FIELD OF TECHNOLOGY

The following relates to a heat exchanger system comprising at least one compressor, at least one condenser, at least one pressure reduction means such as an expansion valve, at least one evaporator, at least one heat exchanger for heating the suction gas between the evaporator and the compressor inlet, which heat exchanger is heated by the refrigerant.

BACKGROUND

U.S. Pat. No. 6,523,365 B2 discloses an accumulator with an internal heat exchanger for use in an air conditioning or refrigeration system having a compressor, a condenser, an expansion device, and an evaporator. In operation, the accumulator is placed in the system so high pressure, high temperature refrigerant flowing from the condenser and low pressure, low temperature refrigerant flowing from the evaporator simultaneously enters and flows through the heat exchanger disposed in the accumulator, whereby the low pressure, low temperature refrigerant absorbs heat and thereby cools the high pressure, high temperature refrigerant. In one embodiment, the heat exchanger comprises a tube having at least one high temperature channel and one low temperature channel extending through the interior of the tube. In a second embodiment, the heat exchanger comprises a single spirally wound coaxial tube having an outer tube and an inner tube positioned within the outer tube. In a third embodiment, the heat exchanger comprises a plurality of coaxial tubes, each coaxial tube having an outer tube and an inner tube positioned in the outer tube wherein the inner tubes are fluidly connected.

SUMMARY

An aspect relates to achieving dry suction gas from a flooded evaporator.

It is a further aspect of the invention to achieve heat exchange with a minimum flow restriction. It is a further aspect of the invention to achieve evaporation of liquid contained in the suction gas.

The aspects can be fulfilled by a system as disclosed in the opening paragraph and by a heat exchanger comprising a circulating path for the suction gas and for the refrigerant liquid.

A heat exchanger for heating suction gas, the heat exchanger is heated by the refrigerant liquid, characterised in that the heat exchanger comprises a circulating path for the suction gas and for the refrigerant liquid, wherein the circulating path is formed with a surface between the suction gas and the refrigerant liquid, such that the circulation of the suction gas will force liquid particles in the suction gas to be forced outside in the circulating path and in that way come in direct thermal contact with the surface that separates the suction gas from the refrigerant liquid.

A heat exchanger is used to transfer heat for example between suction gas and liquid. Heat exchanger can be used in both cooling and heating processes. The liquids and/or gasses are separated by a surface. The surface may be provided with a smooth surface or a ruffled surface, depending on the purpose of the surface.

A heat exchanger for heating suction gas, wherein the heat exchanger also is capable of producing dry suction gas. The dry suction gas is a gas wherein the liquid particles are reduced to a minimum, the liquid particles are substantially removed from the suction gas. The suction gas is for example heated such that the liquid particles in the suction gas may be reduced or removed from the suction gas. The heat exchanger heating suction gas may be arranged between the evaporator and the compressor inlet. The heat exchanger is heated by the refrigerant liquid. The heat exchanger comprises a circulating path for the suction gas and a circulating path for the refrigerant liquid. The suction gas circulating path and the circulating path for the refrigerant liquid are formed with a surface between the suction gas and the refrigerant liquid. The circulation of the suction gas is forcing liquid particles in the suction gas towards the surface. In that way the liquid particles come in direct thermal contact with the surface that separates the suction gas from the refrigerant liquid.

A heat exchanger for heating suction gas and providing dry gas. Hereby it can be achieved that the circulating path forms a highly effective heat exchanger. Of course, the circulating path must be formed so that there is a separation between the suction gas and the refrigerant liquid. The circulating path can be achieved with a very large heat-transmitting surface. The circulation of the suction gas will force liquid particles in the suction gas to be forced outside in the circulating path and in that way come in direct thermal contact with the surface that separates the suction gas from the refrigerant liquid. Hereby it can be achieved that all liquid particles contained in the suction gas will be evaporated during the passage of the circulating path. By this highly effective evaporation of liquid particles in the suction gas, it is possible to use flooded evaporators, which can be totally flooded because afterwards the suction gas is leaving the evaporator. The rest of the liquid that is contained in the suction gas will afterwards be evaporated in the heat exchanger. In that way, the pending patent application discloses a system where evaporators can be used one hundred percent, because they can be totally flooded. In prior art cooling systems flooded evaporators are only flooded up to max 80-90% in systems operating with piston compressors.

In an embodiment of the invention, the heat exchanger comprises an inner tube and a directing plate winded around the inner tube, wherein the suction gas is forced to circulate along the directing plate around the inner tube, and in that way come in direct thermal contact with the surface that separates the suction gas from the refrigerant liquid.

In an embodiment of the invention, the circulating path can be formed in a tank by a number of directing plates for generating a circulating path. The tank further comprises a heat exchanger formed as a plate heat exchanger. Hereby it can be achieved that the directing plates forces the suction gas to circulate inside a heat exchanger. The circulation of the suction gas forces liquid particles in the suction gas into contact with the heat exchanger.

In an embodiment for the invention, the circulating path can be formed in a tank, which tank comprises a hollow screw. The hollow screw comprises a surface which may be an uneven surface. Inside the hollow screw is the refrigerant liquid adapted to circulate, outside the hollow screw is the suction gas adapted to circulate. Hereby it can be achieved that the hollow screw has a very large surface. The screw can be formed so that the suction gas is entering the screw in the top and the suctions gas has to follow the screw with several turns into the bottom of a tank. The suction gas will therefore follow the circulating path defined by the screw. Inside the screw is the warm refrigeration liquid circulating, which is coming directly from the condenser. All liquid particles that will come in touch with the hollow screw will be heated and in that way there will be performed evaporation. Because the hollow screw is extremely long, it is possible to evaporate liquid particles up to more than 10% in the suction gas. Hereby it is achieved that evaporators can be totally flooded and in that way evaporators can be very effective.

In an embodiment of the invention, the directing plate is in a predefined distance to the threaded surface that separates the suction gas from the refrigerant liquid.

Hereby it can be achieved that the circulating path forms a highly effective heat exchanger. The circulation of the suction gas forces the liquid particles in the suction gas towards the threaded surface, wherein the liquid particles come in direct thermal contact with the threaded surface and thereby are separated from the suction gas. Because the hollow screw is extremely long, it is possible to provide efficient evaporation of liquid particles from the suction gas, and thereby provide a dry suction gas.

The surface may be provided with substantially circular recesses and/or protrusions. The recesses and/or protrusions may be formed as a thread on the surface between the suction gas and the refrigerant liquid.

The heat exchanger may comprise at least one directing plate winded around the inner tube. The suction gas is forced to circulate along the winded directing plate or plates. In that way will the liquid particles come in direct thermal contact with the surface and be separated from the suction gas.

The heat exchanger may comprise at least two directing plates. The first winded directing plate may be arranged in a top section of the heat exchanger and forms the circulating path just after the inlet. A second winded directing plate may be arranged in the middle section of the heat exchanger. The second winded directing plate may be an extension of the first winded directing plate, wherein the slope of the first winded directing plate differs from the second winded directing plate. This will provide a relatively low-pressured suction gas in the inlet, and a relatively low-pressured suction gas in the outlet. In the middle part of the circulation path, the pressure is higher than at the inlet and the outlet. In that way will the thermal contact be more efficient when the liquid particles are forced towards the threaded surface. The heat exchange has therefore a minimum flow restriction. Hereby it is achieved that the heat exchanger can handle the suction gas and, in that way, provide an evaporation which increases the efficiency of the heat exchanger.

The hollow screw may comprise a winded tube which is arranged adjacent to the inner side of the tank forming a spiral or a coil-like tubing for the refrigerant liquid. The surface is the surfaces formed by the winded tube. The outer surface of the winded tube has a similar function, wherein the refrigerant liquid heats the suction gas, and thereby extract/evaporate the liquid particles form the suction gas, providing a dry suction gas in the process.

In an embodiment of the invention, a pitch of the directing plate is larger than the pitch of the threaded crest on the threaded surface.

A pitch may for example be measured between threaded crests on the threaded surface. If the distance between the two threaded crests is increased, the slope of the thread is also increased, and vice versa. The slope of the directing plate may be larger than the slope of the threaded crest on the threaded surface. The directing plate is therefore arranged next to/adjacent to the surface. A contact point is the point where the directing plate is nearest the surface. The directing plate with a predefined distance between the threaded surface and the directing plate, increasing the efficiency of the evaporating process.

In an embodiment for the invention the tank can comprise an inlet for the refrigerant liquid and an outlet for the refrigerant liquid, which tank comprises an inlet for the suction gas and an outlet for the suction gas. Hereby it can be achieved that the tank containing the hollow screw is connected to the evaporator for inlet of suction gas and connected to the suction side of the compressor at the outlet of the suction gas. Further, the tank is connected to the condenser and refrigerant liquid is sent from the tank through an expansion valve to the evaporator.

In an embodiment for the invention the tank can comprise an oil outlet. Hereby it can be achieved that oil drops that is collected in the suction gas flows into the tank and circulates outside the hollow screw, where the oil drops will flow at the outside of the screw and probably these oil particles will follow the screw downwards and end in the bottom of the tank. From the bottom of the tank, oil can in different way be transported back to the compressor, where oil is needed for lubrication. Some cooling systems will include a pump that can perform the transport of the oil back to the compressor. In large evaporator systems, where for example screw compressors are used, oil separation and return of oil is very important.

The aspect can also be fulfilled by a method for operating a heat exchange system as previous disclosed, where the compressor generates pressure in a refrigerant gas, which gas is condensed in a condenser to a refrigerant liquid, which liquid is sent to at least one evaporator through a pressure reduction means such as an expansion valve, where a heat exchanger for heating the suction gas is placed between the evaporator and the compressor inlet, which heat exchanger is heated by the refrigerant liquid, where the heat exchanger forces the suction gas into a circulating path for the suction gas, and the heat exchanger forces the refrigerant liquid to heat the suction gas.

Hereby it can be achieved that a highly effective evaporation of liquid gas particles contained in the suction gas will be evaporated. By use of a highly effective heat exchanger, it is possible to use a totally to flood evaporators. Even if there are several percentages of liquid particles in the suction gas, these liquid particles will be evaporated in the circulating path for the suction gas. The gas is circulating easily, but liquid particles will be forced in contact with the walls, and if the walls are in contact with the liquid refrigerant, a slight heating is performed which will evaporate the liquid particles in the suction gas.

In an embodiment for the invention the suction gas can be forced into the circulating path at the outside of a hollow screw, and inside the hollow screw the refrigerant liquid can be forced to circulate. Hereby it can be achieved that the hollow screw can be formed with a very large surface. The suction gas will follow the circulating path defined by the screw. Inside the screw warm refrigerant liquid can be circulating, which is coming directly from the condenser. All liquid particles that will come in touch with the hollow screw will be heated and in that way there will be performed evaporation. Because the hollow screw is extremely long, it is possible to evaporate liquid particles up to more than 10% in the suction gas. Hereby it is achieved that evaporators can be totally flooded and in that way be very effective.

A heat exchanger is a part of a system used to transfer heat for example between suction gas and liquid. The heat exchanger and the heat exchanging system can be used in both cooling and heating processes. The cooling or heating processes may depend on the predefined inlet temperature of the liquid and/or the predefined outlet temperature of the liquid. The cooling or heating processes may also depend on the predefined inlet temperature of the suction or discharge gas and/or the predefined outlet temperature of the suction or discharge gas. The liquids and/or gasses are separated by a surface.

The invention has now been explained with reference to a few embodiments which have only been discussed in order to illustrate the many possibilities and varying design possibilities achievable with the heat exchanger and a heat exchange system according to the present invention.

The invention achieves to provide a solution for a heat exchanger and a heat exchange system, which produce dry suction gas from a flooded evaporator. The invention also achieves to provide a solution for a heat exchanger having a minimum flow restriction. The invention furthermore achieves to provide an evaporation of liquid contained in the suction gas.

BRIEF DESCRIPTION

Some of the embodiments will be described in detail, with references to the following Figures, wherein like designations denote like members, wherein:

FIG. 1 shows a heat exchanger system;

FIG. 2 shows a sectional view of a small section of the tank;

FIG. 3 a shows a possible embodiment for a cooling system;

FIG. 3 b shows a possible embodiment for a heat exchanger system;

FIG. 4 shows a sectional view of a section of a tank;

FIG. 5 shows a sectional view of a section of a tank comprising a circulating path;

FIG. 6 shows a sectional view of a section of a tank with a large hollow screw; and

FIG. 7 shows a sectional view of a section of a tank with two winded directing plates.

DETAILED DESCRIPTION

The embodiments of the invention are explained in the following detailed description. It is to be understood that the invention is not limited in its scope to the following description or as illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways.

FIG. 1 shows a heat exchanger in a cooling system as disclosed in U.S. Pat. No. 6,523,365 B2. FIG. 1 shows a heat exchanger in a cooling system 2 with a compressor 4, which compressor has an inlet 5. The outlet from the compressor leads to a condenser 8, from which condenser refrigerant liquid is sent to a heat exchanger 18 placed in a tank 24. From the tank 24 refrigerant liquid 10 is sent through tubes to a pressure reduction means 14, probably formed as an expansion valve 16. From the expansion valve 16, refrigerant liquid is sent to at least one evaporator 12. From the evaporator 12, the suction gas 20 is sent to the heat exchanger 18. From the heat exchanger 18, the suction gas is sent to the compressor inlet 5.

If the system is a heating system, the heating system would depend on the predefined inlet temperature of a discharge gas and/or the predefined outlet temperature of the discharge gas. The heating system would also depend on the predefined inlet temperature of the liquid and/or the predefined outlet temperature of the liquid in the heat exchanger. The main issue is the system comprising a heat exchanger which heats or cools the gas or liquid inside the heat exchanger 18 with a liquid. The heat exchanger comprises a circulating path for the gas and for the liquid, both in a cooling system and in a heating system. The circulating path is also formed with a surface between the gas and the liquid, such that the gas is in direct thermal contact with the surface that separates the gas with the liquid.

FIG. 2 shows a sectional view of a small section of the tank 24. The sectional view is only to show the principles. FIG. 2 shows an inlet 10 for refrigerant liquid to a tube 32 to the inner 28 of the hollow screw 26. An outlet 34 shows that the refrigerant liquid is sent further in the system. Outside 30 the hollow screw 26, the suction gas is circulating, which has an inlet 36 and an outlet 38. The suction gas is forced to circulate along the hollow screw downwards. The tank can comprise an oil outlet 40.

FIGS. 3 a and 3 b are partly overlapping and disclose a possible embodiment for a heat exchanger system 102. The figures show a compressor module 104 with a compressor inlet line 105. The compressor module 104 has a pressure outlet 107, which is connected to a condenser 108. The condenser 108 is connected to a tank 124 via a pressure line 132, where the refrigerant liquid 110 is passing a circulating path inside the tank 124. The refrigerant liquid 110 leaves the tank 124 to a line 134, and the refrigerant liquid 110 is sent to an expansion valve 116, before the expanded refrigerant is sent to the evaporator 112. From the evaporator 112 the suction gas 120 is sent to a pressure line 136 into the tank 124 and into a circulating path 122 placed inside the tank 124. In the tank 124 the suction gas is slightly heated by the refrigerant liquid 110 that is passing through the line 132 to the line 134. The suction gas 120 is leaving the tank by a connection 138, where the suction gas 105 is sent into the compressor. The tank 124 comprises an oil outlet 140 connected to an oil valve 142. Further is indicated an oil valve 144 connected to the evaporator 112. The two oil lines are connected to a valve lock 146. The outlet from the valve lock 146 goes into an oil ejector 150, where the line 152 is connecting into the oil sump 181. The oil ejector 150 is further connected to a line 148, which is directly connected to the pressure line internally in the compressor module 104. The evaporator 112 comprises an evaporator customer outlet 160. Further, the evaporator 112 is connected to an evaporator customer inlet 162. The condenser 108 comprises a cooling media inlet 164 and a cooling media outlet 166. The cooling media inlet 164 is connected to a magnetic valve 168 and further to a cooling media pump 170. Further, line 172 is connecting the cooling media to the compressor 104, first to pass through an oil cooler 180. Further, the cooling media is sent into the compressor pump device 184 and to the electrical motor 186, from which electrical motor 186 the cooling media in a line 174 return to the cooling media outlet 166. Internally in the compressor block 104, a pressure sensor 188 and a temperature sensor 190 are further indicated. Further are indicated an oil sump 181 and an oil line 182 towards the compressor head covers 184. Further, at the pressure outlet of the compressor is indicated a pressure sensor 192, a temperature sensor 194, and a pressure switch 196.

In operation a system as disclosed in FIGS. 3 a and 3 b , there will of course be an electronic control system, which at least are connected to the different sensors and also send control signals to all the different electronic valves. The electronic device comprises a variable frequency drive 187 in order to generate variable frequencies to the motor. In that way, the motor and also the compressor will be able to operate with different capacity. This can be very important if the load of the heat exchanger system varies. The evaporator outlet 160 could in fact be connected to a plurality of cooling devices, for example in a supermarket. Because the evaporator is formed as a heat exchanger, the media flowing in the connection 160 could be quite different from the refrigerant operating in the heat exchanger system. Probably, the media in the line 160 could be carbon dioxide, which could be used as cooling media in for example a supermarket or in a production of for example meat. Other possibilities to send to the heat exchanger in the evaporator could be a brine, which is a salt contained in water, which can be a highly effective cooling media, for example inside the building.

FIG. 4 shows a sectional view of a section of a tank 24. The heat exchanger 18 forms a plate heat exchanger with refrigerant liquid flowing inside the volume 26. The suction gas 20 is circulating around the inner tube 38 and the gas is forced to circulate by directing plates 23. The inner tube 38 and the directing plate or plates 23 may be formed as an auger. The directing plate 23 is winded around the inner tube 38, and thereby providing a circulating path 22 for the suction gas.

The suction gas is forced to circulate along the directing plate 23 around the inner tube 38, and in that way comes in direct thermal contact with the surface that separates the suction gas from the refrigerant liquid.

In operation the suction gas in the tank 24 will be let in at the top (FIG. 2 ) and the inlet can be placed tangential to the wall of the tank 24, whereby a circulating starts. The circulation is further achieved by directing plates 23. The circulation of the suction gas 20 results in that all liquid particles such as non-evaporated drops of refrigerant or drops of oil are forced into the heat exchanger 18. In the heat exchanger 18 the temperature of the refrigerant liquid 10 will start evaporation of the liquid drops of refrigerant. The tank is so effective that flooded evaporators can be full flooded because this system can accept up to 10% liquid in the suction gas.

The suction gas is forced to circulate along the directing plate 23 around the inner tube 38, and in that way come in direct thermal contact with the surface that separates the suction gas from the refrigerant liquid. The surface as a function as a large heating plate.

A refrigerant could be ammonia, but other media could also be used, for example carbon dioxide.

FIG. 5 shows a sectional view of a section of a tank comprising a circulating path. The heat exchanger 18 is formed in or as a tank 24. The heat exchanger comprises a top section 50, a bottom section 48 and a middle section 49. The inlet 36 for the suction gas 20 is arranged in the top section 50 of the tank. The hollow screw 26 is arranged in the middle section 49 of the tank 24. The hollow screw comprises a surface between the suction gas 20 and the refrigerant liquid 10. An oil outlet 40, not showed in the FIG. 5 , may be arranged in the bottom section 48 of the tank 24.

The heat exchanger heats the suction gas 20 inside the heat exchanger 18 with the refrigerant liquid 10. The heat exchanger 18 comprises a circulating path 22 for the suction gas 20 and for the refrigerant liquid 10. The heating suction gas is heated by the refrigerant liquid 10. The heat exchanger 18 comprises a circulating path 22 for the suction gas 20 and for the refrigerant liquid 10.

The heat exchanger 18 comprises an inner tube 37. The circulating path 22 is formed around the inner tube 37. The inner tube 37 is hollow, such that the inner tube 37 can be used as an outlet 38 for the suction gas 20.

The circulating path is formed with a surface between the suction gas and the refrigerant liquid. The surface 42 is a threaded surface. The circulation of the suction gas 20 will force liquid particles in the suction gas outside in the circulating path 22. In that way the liquid particles will come in direct thermal contact with the threaded surface that separates the suction gas 20 from the refrigerant liquid 10. The treaded surface will lead the liquid particles to the bottom of the heat exchanger 18, e.g., using gravity. The liquid particles may then be removed from the heat exchanger 18. The suction gas leaving through the outlet 38 in inner tube 27, will be dry suction gas.

The heat exchanger comprises a directing plate 23 winded around the inner tube 37. The suction gas is forced to circulate along the winded directing plate 23 around the inner tube 37, and in that way comes in direct thermal contact with the surface 42 that separates the suction gas 20 with the refrigerant liquid 10. The refrigerant liquid 10 is flowing in the inside 28 of the hollow screw 26, between the back wall 44 and the threaded surface 42. A pitch of the directing plate 23 is defined by two overlaying points 23, 23″ of the directing plate 23. A contact point 45 is a predefined distance between the threaded surface 42 and the directing plate 23.

FIG. 6 shows a sectional view of a section of a tank with a large hollow screw. The heat exchanger 18 comprises a top section 50, a bottom section 48 and a middle section 49. The inlet 32 for the refrigerant liquid 20 is arranged in the top section 50 of the heat exchanger 18. The hollow screw 26 is arranged in the middle section 49 of the heat exchanger 18. The outlet 34 for the refrigerant liquid 10 is arranged at the bottom section 48 of the heat exchanger 18. The refrigerant liquid 10 flows from the inlet 32 through the inside 28 of the hollow screw 26, and out of the heat exchanger 18 through the outlet 34 in the bottom section 48.

The directing plate 23 is in a predefined distance to the threaded surface 42, that separates the suction gas 20 with the refrigerant liquid 10. The directing plate 23 has a slope different from the threaded surface 42. A predefined distance is arranged between the directing plates 23 and the threaded surface 42.

A pitch of the threaded crest 46 is measured between two adjacent threaded crests 46. The pitch of the directing plate 23 is larger than the pitch of the threaded crest 46 on the threaded surface 42. The inside 28 of the hollow screw 26 is determined by the distance between threaded crests 46 and threaded root 47, and pitch of the threaded crest 46 and the width of the threaded crests 46 between the threaded roots 47. The amount of refrigerant liquid 10 flowing through the hollow screw 26 is determined by the volume of the inside 28 and the pressure applied to the refrigerant liquid 10 during the cooling process.

FIG. 7 shows a sectional view of a section of a tank with two winded directing plates. Hereby it can be achieved that the circulating path forms a highly effective heat exchanger. The circulation of the suction gas 20 will force liquid particles in the suction gas 20 to the outside of the circulating path. The liquid particles will be captured between the threaded crests 46 and the threaded root 47, when the liquid particles come in direct thermal contact with the threaded surface and thereby are separated from the suction gas. All liquid particles that will come in touch with the hollow screw will be heated, and in that way, there will be performed evaporation. Because the hollow screw is extremely long, it is possible to evaporate liquid particles from the suction gas and thereby provide a dry suction gas. Hereby it is achieved that evaporators can be totally flooded and in that way be very effective.

A first winded directing plate 23 a is arranged in the top section 50 of the heat exchanger 18, such that the circulating path 22 is formed just after the inlet 36. A second winded directing plate 23 b is arranged in the middle section 49 of the heat exchanger 18. The second winded directing plate 23 b may be an extension of the first winded directing plate 23 a. The slope of the first winded directing plate 23 a differs from the second winded directing plate 23 b. This will provide a relatively lower pressure of the suction gas in the inlet and a relatively lower pressure of the suction gas in the outlet than the pressure in the middle part of the circulation path. When increasing the pressure in the circulation path at the second winded directing plate 23 b, the liquid particles in the suction gas will be forced towards the threaded surface in a more efficient manner, due to the increased pressure in the circulating path. In that way will the thermal contact be more efficient when the liquid particles are forced towards the threaded surface. Hereby it is achieved that the heat exchanger can handle the suction gas and, in that way, provide an evaporation which can be very effective.

Although the present invention has been disclosed in the form of embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements. The mention of a “unit” or a “module” does not preclude the use of more than one unit or module.

LIST OF REFERENCE SIGNS

-   Heat exchanger system (2) -   Compressor (4) -   Compressor inlet (5) -   Condenser (8) -   Refrigerant liquid (10) -   Evaporator (12) -   Pressure reduction means (14) -   Expansion valve (16) -   Heat exchanger (18) -   Suction gas (20) -   Circulating path (22) -   Directing plates (23) -   Formed in a tank (24) -   Hollow screw (26) -   Inside (28) the hollow screw (26) -   Outside (30) the hollow screw (26) -   Inlet (32) for the refrigerant liquid (10) -   Outlet (34) for the refrigerant liquid (10) -   Inner tube (37) -   Inlet (36) for the suction gas (20) -   Outlet (38) for the suction gas (20) -   Oil outlet (40) -   Threaded surface (42) Back wall (44) of the hollow screw (26) -   Contact point (45) -   Threaded crest (46) -   Threaded root (47) -   Bottom section (48) -   Middle section (49) -   Top section (50) -   Heat exchanger system (102) -   Compressor (104) -   Compressor inlet (105) -   Compressor outlet (107) -   Condenser (108) -   Evaporator (112) -   Expansion valve (116) -   Suction gas (120) -   Circulating path (122) -   Formed in a tank (124) -   Inlet (132) for the refrigerant liquid (10) -   Outlet (134) for the refrigerant liquid (10) -   Inlet (136) for the suction gas (20) -   Outlet (138) for the suction gas (20) -   Oil outlet (140) -   Oil valve (142) -   Oil valve (144) -   Oil valve block (146) -   Line for pressured gas (148) -   Oil ejector (150) -   Oil return line (152) -   Evaporator customer outlet (160) -   Evaporator customer inlet (162) -   Cooling media inlet (164) -   Cooling media outlet (166) -   Magnetic valve (168) -   Coiling media pump (170) -   Cooling media compressor inlet (172) -   Cooling media compressor outlet (174) -   Oil cooler (180) -   Oil sump (181) -   Compressor oil inlet (182) -   Compressor head covers (184) -   Electro motor (186) -   Variable frequency drive (187) -   Pressure sensor (188) -   Temperature sensor (190) -   Pressure sensor (192) -   Temperature sensor (194) -   Pressure switch (196) 

1. A heat exchanger for heating suction gas, the heat exchanger heats suction gas inside the heat exchanger with a refrigerant liquid, wherein the heat exchanger comprises a circulating path for the suction gas and for the refrigerant liquid, wherein the circulating path is formed with a surface between the suction gas and the refrigerant liquid, such that the circulation of the suction gas will force liquid particles in the suction gas in direct thermal contact with the surface that separates the suction gas with the refrigerant liquid.
 2. The heat exchanger according to claim 1, wherein the heat exchanger comprises an inner tube and at least one directing plate winded around the inner tube, wherein the suction gas is forced to circulate along the directing plate around the inner tube, and in that way comes in direct thermal contact with the surface that separates the suction gas from the refrigerant liquid.
 3. The heat exchanger according to claim 2, wherein a first winded directing plate is arranged in a top section of the heat exchanger, and a second winded directing plate is arranged in the middle section of the heat exchanger.
 4. The heat exchanger according to claim 2, wherein the slope of the first winded directing plate differs from the second winded directing plate.
 5. The heat exchanger according to claim 2, wherein the second winded directing plate is an extension of the first winded directing plate.
 6. The heat exchanger according to claim 1, wherein the surface is a threaded surface.
 7. The heat exchanger according to claim 2, wherein the directing plate is in a predefined distance to the threaded surface.
 8. The heat exchanger according to claim 4, wherein a slope of the directing plate is larger than the slope of the threaded crest on the threaded surface.
 9. The heat exchanger system comprising at least one compressor, at least one condenser, at least one pressure reduction means such as an expansion valve, at least one evaporator, at least one heat exchanger for heating the suction gas between the evaporator and the compressor inlet, which heat exchanger is heated by the refrigerant liquid, wherein the heat exchanger comprises a circulating path for the suction gas and for the refrigerant liquid, wherein the circulating path is formed with a surface between the suction gas and the refrigerant liquid.
 10. The heat exchanger system according to claim 9, wherein the circulating path is formed in a tank, by a number of directing plates for generating a circulating path.
 11. The heat exchanger system according to claim 9, wherein the circulating path is formed in a tank, which tank comprises a hollow screw, inside the hollow screw is the refrigerant liquid configured to circulate, outside the hollow screw is the suction gas configured to circulate.
 12. The heat exchanger system according to claim 10, wherein the tank comprises an inlet for the refrigerant liquid and an outlet for the refrigerant liquid, which tank comprises an inlet for the suction gas and an outlet for the suction gas.
 13. The heat exchanger system according to claim 10, wherein the tank comprises an oil outlet.
 14. A method for operating a heat exchanger system according to claim 9, wherein the compressor generates pressure in a refrigerant gas, which gas is condensed in a condenser to a refrigerant liquid, which liquid is sent to at least one evaporator through a pressure reduction means such as an expansion valve, where a heat exchanger for heating the suction gas is placed between the evaporator and the compressor inlet, which heat exchanger is heated by the refrigerant liquid, wherein the heat exchanger forces the suction gas into a circulating path for the suction gas, and the heat exchanger forces the refrigerant liquid to heat the suction gas.
 15. The method according to claim 14, wherein the suction gas is forced into the circulating path at the outside of a hollow screw, and inside the hollow screw is the refrigerant liquid forced to circulate. 